By any measure BHP's Billiton's plan to take over Rio Tinto is extraordinary. The proposal, which was flushed out by leaks on Thursday, would be the second largest corporate merger in history, creating one of the world's top five companies valued at around $400 billion with annual sales of $100 billion.

While Rio has rebuffed the initial three-for-one share swap, worth $120 billion, there's little doubt that this is only the first step in a collossal struggle. And reports carried in London's Financial Times that BHP had secured a $70 billion financing package indicate that a hostile bid including cash is not out of the question.